1 Genome Center of Wisconsin, University of Wisconsin, Madison, WI 53706, USA; Department of Chemistry, University of Wisconsin, Madison, WI 53706, USA.
2 Genome Center of Wisconsin, University of Wisconsin, Madison, WI 53706, USA.
3 Genome Center of Wisconsin, University of Wisconsin, Madison, WI 53706, USA; Department of Chemistry, University of Wisconsin, Madison, WI 53706, USA; Department of Biomolecular Chemistry, University of Wisconsin, Madison, WI 53706, USA. Electronic address: jcoon@chem.wisc.edu.